1. Field of the Invention
The present invention relates to a water cutoff structure of a covered wire used in a wire harness of an automobile or the like. Specifically, the invention relates to a structure achieving water cutoff to the covered wire by sandwiching the covered wire constituted by covering core lines by a water cutoff member made of a resin to subject to ultrasonic welding.
2. Related Art
According to a wire harness of an automobile, water may continue invading via clearances among core lines of a covered wire, thereby, water may reach inside of an apparatus of a control unit or the like. In order to prevent the invasion, a wire harness used at a portion at which water may invade is normally provided with a water cutoff structure.
As an example of a water cutoff structure of this kind, there is known a constitution of sealing clearances among core lines of a terminal of an electric wire by enveloping a portion of connecting the terminal of the electric wire exposed to a portion at which water may invade by a thermally contractible tube with hot melt and molding the terminal connecting portion by hot melt (for example, refer to JP-A-2000-182688, page 2, FIG. 3).
Further, as shown by FIG. 11, there is also an example of creating a structure in which when electric wires are connected by utilizing ultrasonic vibration, water cutoff can be carried out at the same time. According to the example, when covered wires 1 and 2 are connected, the two electric wires 1 and 2 are overlapped at a connecting portion 3. Further, a cover resin is melted and resin chips 4 and 5 are melted together by sandwiching the overlapped connecting portion 3 by a pair of the resin chips 4 and 5 and applying ultrasonic vibration to the resin chips 4 and 5 while pressing the resin chips 4 and 5 from outer sides. At that occasion, the structure capable of carrying out water cutoff is finished by filling the molten resin among the core lines at a vicinity of the connecting portion (for example, refer to JP-A-7-320842, page 4, FIG. 1 and JP-A-11-250952).
According to the related art in which the terminal connecting portion is enveloped by the thermally contractible tube and molded by hot melt, a number of steps are taken and therefore, the operation is troublesome. Further, the constitution of sandwiching the electric wire connecting portion by the resin chips is inherently a technology when two pieces of electric wires are connected and therefore, it is difficult to ensure high water cutoff performance.